Use of small thinning logs in a round-wood trussed bridge

摘要

The purpose of this study was to determine the flexural properties of a truss system fabricated with thinnings from a Taiwania plantation and their application to pedestrian bridge construction. The maximum bending capacity at failure of a 6-m truss system fabricated with round-wood members 150 mm in diameter is 1.7 times that fabricated with 120 mm diameter members, and 2.4 times that of a 4-m truss system with 120-mm members. The yield bearing strength of single and double bolted joints for 120 and 150 mm round wood members ranges from 73 percent to 85 percent of maximum dowel bearing strength. The maximum load capacity of bolted joints for 120 and 150 mm round wood members was 5.5 times and 5.4 times the allowable design value. The flexural deflection of a trussed pedestrian bridge subjected to dead load and live load of 3924 N/m2 was L/416, which met the code criteria of L/300. The creep behavior of a 6-m pedestrian bridge was in steady stage after 2 months of live loads, and the flexural deflection reached 90 percent of that measured after 6 months. The MC of chord members after the trussed bridge had been completed for 6 months dropped to between 23.6 to 29.2% from the initial green state.